I suppose this is a bad time to mention, I actually enjoy Kalista. Annoying, but good for the game, having an ADC that scales with AS instead of crit is a good step imo. I'll admit, it's been ages since I went against a good Kalista, and I rarely play Singed / Volibear, beyond the point though.
I'm starting to assume that for the most part, Riot tends to avoid suggestions pre-rework phase. Similar circumstances happened with Cass, and I'll assume other champions before. In turn, Cass did undergo numerous changes before this live version, and Mordekaiser did get a poor self casted W back. Neither was everything the community wanted, but it was something.
Q was always impossible to use with his mobility. It was mainly wave clear, or excess poke against melees. It was incredibly rare for a ranged mid to be close enough to get splashed by the AOE. The change seems more like a power shift then a nerf imo, but opinions. I'll admit, I do enjoy the rework, more from the fact that he's more based around getting a ghost, and holding it, but dragons pretty cool as well.
Win rates, statistics. I love these things. Which site do you use? I know a lot of people lost faith in Champion.gg after their first mistake with Mordekaiser, and I kind of question if that has happened again. But, assuming that they're accurate, mid mordekaiser has completely fallen off. Now, I have to wonder why. 62% ban rate might be a cause, coupled with the assumption that he's only viable as a duo laner. Still, I doubt that the playstyle completely fell off. I'm not sure this is the best patch to look at statistics for honestly. Riot made a statement somewhere that they believe Darius is fine, and want to wait out, so that people can play against him and realize that.
Again, I'm getting off topic. It's a shame you're on EUNE, and a lot of other people complaining about Morde aren't on NA. I'd be more than willing to play a game or two, and see if Morde was still viable in other lanes.